Photoresponsiveness of Anthracene-Based Supramolecular Polymers Regulated via a σ-Platinated 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene Photosensitizer

Anthracene and its derivatives have attracted tremendous interest in recent years because of their intriguing photoresponsive behaviors. Our research group has previously constructed anthracene-based supramolecular polymers, which display multicycle anthracene-endoperoxide photo switching in a macroscopic manner. However, high-energy light excitation (lambda = 365-460 nm) is required for anthraceneto-endoperoxide photooxygenation, giving rise to severe photodegradation problems. In this work, we have developed an effective approach to addressing this issue, by encapsulating a sigma-platinated 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) photosensitizer into anthracene-based supra molecular polymeric systems. The platination effect enhances pi-electron delocalization, while promoting intersystem crossing from singlet to triplet excited states. Accordingly, the sigma-platinated BODIPY photosensitizer displays excellent O-1(2) production capability, facilitating anthracene-to-endoperoxide transformation under low-energy irradiation conditions (lambda = 520-590 nm). This leads to the breakup of supramolecular polymers and gels, which can be restored at room and elevated temperatures because of the reversible endoperoxide-to-anthracene deoxygenation process. Overall, the rational design of a sigma-metalated photosensitizer opens up a new avenue to regulating the photoresponsiveness of supramolecular polymers under mild and nondestructive conditions.